The use of plastics or other materials to create form fitting objects requires precise development and manufacturing processes. Common form fitting objects typically include medical products like hearing aids, prosthetics or clear aligners for repositioning teeth.
The use of clear, plastic-type aligners for the re-positioning of teeth is becoming increasingly popular. Such aligners are typically produced by forming a plastic material over stereolithography (SLA) molds that represent various stages of treatment of a patient's orthodontic treatment. After forming the aligner material over a mold, the cutting of the aligner material occurs on the gingival surface along the interproximal area, i.e., a region that is proximate the gingival surface between the teeth and gums, to define the plastic aligner from the SLA molds. Conventional methodologies for creating such a cutting curve have various drawbacks.
For example, in many instances, the cutting curve has too many straight lines between the interproximal areas, with such straight line portions unable to provide sufficient resistance force to effectively facilitate teeth movement, and potentially cutting into the gingival surface of the patient and causing great pain. In other interproximal areas, a sharp shaped portion of the aligner material can result in stress risers, potentially causing the aligner material to break during treatment.
Manual trimming of the aligner material is also required in many instances, such as the punctured inner shell. As another example, in some cases the interproximal areas can have the cutting curve passing inside the jaw mold that leads to puncturing of the stereolithography (SLA) mold, requiring the SLA mold to be rebuilt and manually trimmed. Manual trimming is also typically required with such conventional processes in treating pontic cases, often requiring pontic cases to be filtered out from automation trimming line before such manual trimming, as well as in the back molar region to address extraneous material produced.
Still further, conventional techniques for generating cutting curves do not suitably address the potential for collisions of a cutting tool within the cutting machine when cutting the aligner material from the SLA molds.